A Self-Cancelling Solution for Inter carrier Interference in OFDM Mobile Communication Networks

Abstract

For orthogonal frequency-division multiplexing (OFDM) communication systems, the frequency offsets in mobile radio
channels distort the orthogonality between subcarriers resulting in intercarrier interference (ICI). This paper studies an efficient
ICI cancellation method termed ICI self-cancellation scheme. The scheme works in two very simple steps. At the transmitter side,
one data symbol is modulated onto a group of adjacent subcarriers with a group of weighting coefficients. The weighting
coefficients are designed so that the ICI caused by the channel frequency errors can be minimized. At the receiver side, by linearly
combining the received signals on these subcarriers with proposed coefficients, the residual ICI contained in the received signals
can then be further reduced. The carrier-to-inter- ference power ratio (CIR) can be increased by 15 and 30 dB when the group size is
two or three, respectively, for a channel with a constant frequency offset. Although the redundant modulation causes a reduction in
bandwidth efficiency, it can be compensated, for example, by using larger signal alphabet sizes. Simulations show that OFDM
systems using the proposed ICI self-cancellation scheme perform much better than standard systems while having the same
bandwidth efficiency in multipath mobile radio channels with large Doppler frequencies.